The present study aims to evaluate the role of heat- preconditioning MSCs in improving the efficacy of treatment of chemically induced fibrosis. To achieve the aim of the study, heat treated stem cells were obtained by isolating adipose-derived stem cells (ADSCs) from rats, and heat treating them at a temperature of 42 °C for an hour to cause heat shock to mesenchymal stem cells (MSCs). Liver fibrosis in rats was induced by thioacetamide (TAA). A group of rats were treated with mesenchymal stem cells (MSCs) and another group with heat treated mesenchymal stem cells (MSCs). To investigate the effect of heat-treated mesenchymal stem cells (MSCs) on liver cells, the liver tissue of the study groups was examined and compared to the control group using Masson Trichrome (MT), Sirius Red dyes. The results of the histological examination showed that TAA caused pathological changes and fibrosis of the liver cells. Significant improvement in hepatocytes and a decrease in fibrosis rates for the livers of rats treated with mesenchymal stem cells (MSCs) pre-treated with heat, compared to the resulting improvement in liver cells of rats treated with mesenchymal stem cells (MSCs) without heat treatment. The study concluded that heat treatment of mesenchymal stem cells improves the therapeutic efficacy of chemically induced liver fibrosis in rats.